Semiconductor array imager for printing systems

Abstract

To provide an independently addressable vertical cavity surface emitting laser (VCSEL) architecture in an imaging array which can generate the high power and support mounting in a tight pitch.SOLUTION: A laser imager for a printing system comprises: a plurality of independently addressable surface emitting lasers arranged in a linear array on a common substrate chip and including a common cathode; a dedicated control channel associated with an address trace line for each laser of the plurality of independently addressable surface emitting lasers; and optical elements arranged in a linear lens array configured to capture and focus light from the plurality of independently addressable surface emitting lasers onto an imaging member, wherein the plurality of independently addressable surface emitting lasers arranged in the linear array and the optical elements arranged in the linear lens array operate together to image the imaging member.SELECTED DRAWING: Figure 24

Description

[Technical Field]

[0001] Embodiments relate to semiconductor laser arrays. Embodiments also relate to semiconductor imager arrays for use in printing systems. More specifically, embodiments relate to providing independently addressable vertical cavity surface emitting laser (VCSEL) architectures in imaging arrays that are capable of producing high power and accommodating tight pitch packaging. [Background technology]

[0002] VCSELs are semiconductor-based lasers that emit light perpendicular to the substrate. When properly designed, technological applications of VCSEL arrays can include data communication systems, light detection and ranging (lidar) systems, printing systems, laser processing systems, zone heating or curing, lighting systems, 3D mapping systems, and facial recognition devices (e.g., smartphone facial recognition).

[0003] High-power surface-emitting lasers typically require large apertures because the device's light-emitting area must be large enough to support the requisite high optical output. For example, a typical aperture for a VCSEL capable of producing 50 mW of optical output must be approximately 18 μm or larger in diameter. The overall device size will be even larger because the device structure typically includes oxide channels and electrical contacts that extend beyond the aperture.

[0004] One of the key advantages of VCSELs is that, when properly positioned, they can be patterned into dense arrays, with hundreds or even thousands of individual emitters acting as pixels. This will be important because some applications require high-power surface-emitting lasers to be implemented in tightly pitched arrays, where the linear pitch is comparable to or smaller than the nominal dimensions of the device. For example, in a 1200 dpi printing application, if each laser pixel in the array is used to address one dot on an image, the required linear spacing between laser address lines would be approximately 21.2 μm. This linear pitch is tighter than the size of current semiconductor laser devices capable of generating 50 mW of optical output. Today's efficient or high-intensity semiconductor lasers often operate in the 550 nm to 1000 nm wavelength range. Due to the very close spacing between lasers in such arrays, thermal crosstalk can be an issue, as heat from each laser can affect the performance of nearby lasers. Additionally, the aggregate power dissipation from many high-power lasers operating within a small area can result in a high heat load density that must be dissipated.

[0005] What is needed is an independently addressable VCSEL architecture that can generate high power at resolutions greater than 300 dpi and accommodate tight pitch implementation while overcoming thermally induced drawbacks. Summary of the Invention

[0006] The following summary is provided to facilitate an understanding of some of the innovative features unique to the disclosed embodiments and is not intended to be a complete description. A complete understanding of the various aspects of the embodiments disclosed herein can be obtained by considering the entire specification, claims, drawings, and abstract together.

[0007] According to embodiments, a semiconductor laser (e.g., VCSEL) architecture is disclosed that can achieve digital addressability of 300 to at least 1200 dpi. This architecture can have features including improved laser array design, improved laser array geometry, and chip tiling. In printing applications, for example, VCSELs according to the present embodiments, operated as pixels and deployed in an array format, can deliver laser powers up to 50 milliwatts and greater, with aperture sizes that can enable high-resolution (e.g., >300 dpi) resolution.

[0008] According to embodiments, semiconductor laser arrays can be used as individually addressable light sources, for example in DALI (Digital Architecture for Lithographic Ink) printing processes, which utilize dramatically reduced size and complexity relative to the most sophisticated component in a printing system: the laser imager.

[0009] According to an embodiment, a laser imager for a printing system can be provided that includes a plurality of independently addressable surface-emitting lasers arranged in a linear array on a common substrate chip and including a common cathode, and a dedicated control channel associated with an address trace line for each laser of the plurality of independently addressable surface-emitting lasers.

[0010] According to an embodiment, the optical elements may be arranged in a linear lens array configured to capture and focus light from multiple independently addressable surface emitting lasers.

[0011] According to an embodiment, a plurality of independently addressable surface emitting lasers arranged in a linear array and optical elements arranged in a linear lens array can work together to image the blanket cylinder.

[0012] According to embodiments, large-area, high-power VCSEL arrays as presented herein may also be useful in a variety of applications, such as facial recognition, laser sintering, non-contact thermochromic printing, zone heating and curing, and lidar applications.

[0013] According to embodiments, the semiconductor laser array can include a mounting and cooling architecture capable of maintaining laser operating temperature and efficiency.

[0014] According to one aspect of the embodiment, the semiconductor laser array can include direct die attach to a 3D submount with integrated cooling channels.

[0015] According to another aspect of the embodiment, the semiconductor laser array can include transferring a VCSEL epilayer onto a metallic host substrate.

[0016] According to another aspect of the embodiment, the semiconductor laser array can implement image frame phase delay addressing.

[0017] According to another feature of the embodiment, the semiconductor laser array can use a SELFOC lens array.

[0018] According to yet another aspect of the embodiment, the semiconductor laser array may be integrated on a 3D submount.

[0019] According to another aspect of the embodiment, the semiconductor laser array can incorporate a multi-row interposer design, including fan-in for ASIC placement tolerance. [Brief explanation of the drawings]

[0020] The accompanying drawings, in which like reference numbers refer to identical or functionally similar elements throughout the separate views and which are incorporated in and form a part of this specification, further illustrate the present invention and, together with the detailed description of the invention, serve to explain the principles of the embodiments. [Figure 1] 1 illustrates the architecture of a 1200 dpi pitch independently addressable high power laser array, according to an embodiment. [Figure 2] 1 illustrates an example block diagram of layouts and dimensions that can be met to achieve high resolution laser processing and imaging goals by staggering placement of bond pads and trace lines, according to an embodiment. [Figure 3] FIG. 1 shows an exemplary block diagram of wirebond connections for individual lasers to their associated driver chips, according to an embodiment. [Figure 4] FIG. 1 shows a block diagram of an 11-inch wide VCSEL imager for a 1200 dpi printing system that may be composed of multiple tiled laser array chips, according to an embodiment. [Figure 5] FIG. 1 shows a block diagram of staggered laser array chips, according to an embodiment. [Figure 6] 1 shows an optical micrograph of a portion of a 1200 dpi laser array utilizing an asymmetric laser aperture design, according to an embodiment. [Figure 7] 10 shows a chart of light output versus current curves for devices at various substrate temperatures, showing peak output powers of over 50 mW, according to an embodiment. [Figure 8] 1 shows an optical micrograph of a portion of a 1200 dpi laser array utilizing a common anode multi-aperture pixel design, according to an embodiment. [Figure 9] 1 shows a chart of light output versus current curves for one two-aperture common anode device at various substrate temperatures, showing peak output powers of over 50 mW, according to an embodiment. [Figure 10A] 1 shows an optical micrograph of a portion of a 1200 dpi laser array utilizing a common anode 3-aperture pixel design, according to an embodiment. [Figure 10B] 10B shows a close-up of the three-aperture pixel of FIG. 10A revealing six levels of staking in the process direction, according to an embodiment. [Figure 11]1 shows a photograph of a back view of a submount, illustrating how cooling fluid conduits can be attached to the submount, and also illustrating how integral mounting holes can be formed in the submount for mounting optical elements, according to an embodiment. [Figure 12A] FIG. 1 shows a front view of a lens array that can be used with a semiconductor laser array. [Figure 12B] FIG. 1 shows a front view of a lens array that can be used with a semiconductor laser array. [Figure 12C] FIG. 1 shows a front view of a lens array that can be used with a semiconductor laser array. [Figure 12D] FIG. 1 shows a three-point perspective view of an imaging optical system including a four-row GRIN lens array that can be used with the VCSEL arrays described herein, according to an embodiment. [Figure 13] 10 shows a graph of calculated optical transmission versus source beam divergence for various laser spatial mode profiles, according to an embodiment. [Figure 14A] 1 is a photograph of a four-row GRIN lens array (GLA) constructed from two modified two-row SLAs, according to an embodiment. [Figure 14B] 14B shows an optical microscope photograph of the combined two rows of GLA of FIG. 14A, according to an embodiment. [Figure 15A] FIG. 1 shows a block diagram of a staggered imaging system for a laser array, according to an embodiment. [Figure 15B] 1 illustrates an example of VCSEL scroll timing using a four-row VCSEL laser array 170 with two apertures, according to an embodiment. [Figure 16] 1 illustrates a feathered imaging system for a laser array, according to an embodiment. [Figure 17] 1 illustrates an electrical thin film routing layout for an interposer chip architecture that fans out tight pitch contact pads on a laser array to wider pitch contacts on a PCB or driver chip, according to an embodiment. [Figure 18A]10 shows a graph of calculated temperature versus substrate thickness at various locations on the surface of a laser chip, according to an embodiment. [Figure 18B] 1 illustrates a layout of a laser chip surface with a temperature profile shown across the surface, according to an embodiment. [Figure 19A] 1 illustrates process steps for transferring epi of a VCSEL array to a metal host substrate, according to an embodiment. [Figure 19B] 1 illustrates process steps for transferring epi of a VCSEL array to a metal host substrate, according to an embodiment. [Figure 19C] 1 illustrates process steps for transferring epi of a VCSEL array to a metal host substrate, according to an embodiment. [Figure 19D] 1 illustrates process steps for transferring epi of a VCSEL array to a metal host substrate, according to an embodiment. [Figure 19E] 1 illustrates process steps for transferring epi of a VCSEL array to a metal host substrate, according to an embodiment. [Figure 20] 1 is labeled as Prior Art and shows a diagram of components of a printing system incorporating a laser array for inducing evaporation of dampening fluid via laser patterning and associated printing steps, according to an embodiment. [Figure 21A] 1 shows a diagram of components of a completed VCSEL array-based imaging member, according to an embodiment. [Figure 21B] FIG. 21B shows a side perspective view of the completed VCSEL array-based imaging member presented in FIG. 21A. [Figure 22] 1 illustrates a block diagram of electronic modules operating as part of a printing system, according to an embodiment. [Figure 23A] FIG. 1 illustrates a block diagram of programming states during printing when using a VCSEL for document processing, according to an embodiment. [Figure 23B] FIG. 1 illustrates a block diagram of programming states during printing when using a VCSEL for document processing, according to an embodiment. [Figure 24]FIG. 1 shows a block diagram representing possible functionality of the major modules of a printing system incorporating the use of a VCSEL array, according to an embodiment. [Figure 25] 1 shows another block diagram illustrating possible functionality of major modules of a printing system incorporating the use of a VCSEL array, according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] The specific values ​​and configurations discussed in these non-limiting examples may be varied and are cited merely to illustrate one or more embodiments and are not intended to limit the scope thereof.

[0022] The present subject matter will now be described in more detail below with reference to the accompanying drawings, which form a part of this specification and which show, by way of illustration, specific exemplary embodiments. However, the subject matter may be embodied in a variety of different forms, and therefore, it is intended that the covered or claimed subject matter be construed as not being limited to any exemplary embodiments set forth herein. The exemplary embodiments are provided for illustrative purposes only. Likewise, a fairly broad scope is intended for the subject matter claimed or referenced. Among other things, for example, the subject matter may be embodied as a method, device, component, or system. Thus, embodiments may take the form of, for example, hardware, software, firmware, or any combination thereof (other than software itself). Accordingly, the following detailed description is not intended to be construed in a limiting sense.

[0023] Throughout this specification and claims, terms may have nuanced meanings suggested or implied in context beyond their explicitly stated meaning. Similarly, as used herein, phrases such as "in one embodiment" or "in an exemplary embodiment," and variations thereof, do not necessarily refer to the same embodiment, and as used herein, phrases such as "in another embodiment" or "in another exemplary embodiment," and variations thereof, may, but do not necessarily, refer to different embodiments. For example, claimed subject matter is intended to include combinations of the exemplary embodiments in whole or in part.

[0024] In general, terms may be understood, at least in part, from their use in context. For example, terms such as "and," "or," or "and / or" as used herein may include a variety of meanings that may depend, at least in part, on the context in which such terms are used. Typically, when "or" is used to relate a list such as A, B, or C, it is intended to mean A, B, and C as used herein in an inclusive sense, as well as A, B, or C as used herein in an exclusive sense. Additionally, as used herein, the term "one or more" may be used to describe any feature, structure, or characteristic in a singular sense, or may be used to describe a combination of features, structures, or characteristics in a plural sense, depending, at least in part, on the context. Similarly, terms such as "a," "an," or "the" may also be understood to convey a singular use or to convey a plural use, depending, at least in part, on the context. Additionally, the term "based on" is not necessarily intended to convey an exclusive set of factors, but instead may be understood as allowing for the presence of additional factors not necessarily explicitly recited, also depending, at least in part, on the context.

[0025] Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structures of the embodiments selected for illustration in the drawings, and are not intended to define or limit the scope of the present disclosure. In the following drawings and the following description, it should be understood that like numerical designations refer to components of similar function.

[0026] Although embodiments are not limited in this regard, as used herein, the terms “plurality” and “a plurality” may include, for example, “multiple” or “two or more.” The terms “plurality” or “a plurality” may be used throughout this specification to describe two or more components, devices, elements, units, parameters, etc. For example, “plurality of stations” may include two or more stations. The terms “first,” “second,” etc. herein do not denote any order, quantity, or importance, but rather may be used to distinguish one element from another. The terms “a” and “an” herein may not denote a limitation of quantity, but rather may indicate the presence of at least one of the referenced items.

[0027] As used herein, the terms "printing device," "printing system," or "digital printing system" may refer to a digital copier or printer, scanner, image printer, digital production press, document processing system, image reproduction machine, bookbinding machine, facsimile machine, or multi-function device, etc., and may include several marking engines, feeding mechanisms, scanning assemblies, and other print media handling units, such as feeders, finishers, etc. Digital printing systems can handle sheets, webs, marking materials, etc. A digital printing system is any machine, or any combination of machines, that can place marks on any surface, etc., and read marks on input sheets.

[0028] As used herein, the term "pitch" may refer to the minimum center-to-center distance between interconnect lines. Because half pitch can approximate the minimum line width, it can be used as an indicator of the integration level of an IC.

[0029] As used herein, the term "semiconductor laser" may refer to a surface-emitting semiconductor laser, such as a VCSEL (vertical cavity surface-emitting laser), that can be fabricated on a semiconductor substrate using semiconductor fabrication techniques.

[0030] When properly designed, current state-of-the-art VCSELs (vertical cavity surface-emitting lasers) are capable of generating enough optical output power to be deployed in array format, and when properly configured and packaged, can be used for high-resolution evaporation of dampening fluid in high-speed printing systems. Such systems require each VCSEL in the array to generate tens of milliwatts of optical output power as a standalone device when operated alone, and require the VCSEL array and its packaging to be designed so that the laser retains its capability even when adjacent devices are turned on simultaneously. Features of embodiments provide, among other things, a unique VCSEL array chip design that can result in high-power, small-pitch individually addressable lasers, methods for mounting, cooling, driving, and imaging, large numbers of VCSEL array chips that enable wide width (>100 mm) printing on a chip, and an example of a VCSEL array used to print in a DALI (Digital Architecture for Lithographic Ink) printing process.

[0031] The VCSEL array chip described herein allows for tightly-spaced implementation of independently addressable, high-power surface-emitting lasers. In some embodiments, the VCSELs share a cathode and are individually addressable through individual address lines connecting the individual VCSEL anodes. In some embodiments, a common-anode addressing architecture can be used, in which each address line in the array can encompass multiple electrically connected apertures. Elongated, asymmetric aperture shapes can also be used to fit within the address line pitch. In addition, laser spacing in the process direction can be accommodated, for example, by the Dali printing process, to increase the total laser distance while still maintaining an effective cross-process spacing that can be smaller than the size of the lasers themselves.

[0032] A "pixel" can refer to a set of VCSELs or a single VCSEL. For example, in Figure 6, a pixel contains one laser. In Figure 8, a pixel contains two lasers coupled together. In Figure 10, a pixel contains a set of three VCSELs.

[0033] The "aggregate linear pitch" referred to herein refers to the cross-process spacing between adjacent cross-process direction lasers, regardless of their position in the process direction. For example, in FIG. 8, the cross-process spacing between Set B and Set C is 21.2 μm. The "laser size" in FIG. 8 is the "width" of the common anode metal contact for Laser Set B.

[0034] Optimized thermal management of VCSEL array chips can be achieved using two specific approaches, which can be used together: a) direct die-attaching to a mechanical block that incorporates slots for the driver chips, means for cooling, e.g., by cooling fluid channels or heat pipes, and means for mounting the optical system, and b) ultra-thin laser epitaxial layers that are transferred to a thermally conductive metal host substrate.

[0035] Stitching of VCSEL array chips can be enabled so that the effective (stitched) laser array width meets today's production print width demands. The effective laser array includes the means to focus the laser light from the VCSELs, drive the individual lasers, cool the lasers, and extract evaporated dampening fluid during DALI printing operations.

[0036] VCSEL array chip design Referring to FIG. 1, an architecture for a 1200 dpi pitch, independently addressable, high-power laser array according to an embodiment is shown. FIG. 1 shows the layout of a linear array 100 of VCSELs 110 with address trace lines 115 having a 21.2 μm pitch. The electrical contact pads 120 must be large enough to allow wire bonding, and the electrical trace lines 115 must be wide enough to allow low sheet resistance and negligible voltage drop when energized with a signal during operation. In the illustrated embodiment, the semiconductor lasers 110 are arranged along two rows, with one set of address lines 115 entering from the top and the other set entering from the bottom. The two rows of lasers are offset relative to each other to form an interdigitated linear array of light emitters on a 21.2 μm pitch. The contact pads 120 on each side can also have a staggered arrangement, so they can be large enough for wire bonding and still fit within the available space between the address lines. Figure 1 shows a 21 mm long by 2 mm wide chip that can contain 1000 lasers. Referring to Figure 2, an exemplary layout 105 and dimensions of bond pads 120 and trace lines 115 that can further meet the objectives shown in Figure 1 are further shown.

[0037] Referring to Figure 3, an exemplary block diagram 130 is shown of wire bond connections 133 of individual VCSELs 110 of each VCSEL array chip 100 to dedicated control channels of an associated driver chip 135, according to an embodiment. The wire bond connections 133 to the respective driver chips 135 can have the same pitch as the laser pitch, or a pitch that varies slightly, e.g., a smaller pitch. Figure 3 shows how the individual laser chips 100 can be connected to their respective driver chips 135 via wire bond connections 133.

[0038] In an exemplary implementation for printing, many laser array chips 100 would be arranged side-by-side along the cross-process (or x) direction of a document 101, as indicated by arrow 103, to form a wide imager 140. FIG. 4 shows a 14-chip arrangement forming an 11-inch wide, 1200 dpi imager 140 for processing images of a document 101 flowing in the process (or y) direction, as indicated by arrow 102. The tiled laser array chips 100 can also have a staggered arrangement 150, as shown in FIG. 5, instead of the linear, side-by-side arrangement shown in FIG. 4, to process images of a document 101 flowing in the process direction 102 as shown. In a staggered design, portions of the print frame corresponding to individual chips receive appropriate timing delays so that the final image formed is stitched correctly. Imperfections in alignment can also be addressed by performing calibration to adjust the relative timing delays of each laser chip 100. In other embodiments, the laser array chips may have dedicated alignment structures to ensure precise alignment of two adjacent laser array chips or precise alignment to a support structure.

[0039] To accommodate the large aperture size, capable of delivering up to 50 mW of optical power per laser, an asymmetric laser aperture design can be utilized instead of the usual circular aperture. The aperture shape can be "squeezed" along the direction of the array, thus fitting within the available space in a tightly pitched arrangement. The aperture can be correspondingly "elongated" in the direction of the address lines to compensate for the squeezed dimensions, so that a sufficiently large emitting area can still be achieved.

[0040] Figure 6 shows an optical microscope photograph of a portion of a 1200 dpi laser array 160 utilizing an oval 8 × 32 μm aperture geometry for the VCSEL light emitters 110. The process direction 102 is indicated by a document icon 101. The light emitters 110 can be arranged in four interdigitated rows 162, with half of the addressing traces coming from the top side and half coming from the bottom side. The emitter apertures can be positioned at different angles so that their cross-process direction width is effectively the same as the emitter pitch (e.g., 21.2 μm). For an 8 × 32 μm aperture geometry, a 50.5-degree angle, for example, would achieve this. Figure 7 shows a graph of the measured optical output versus current curves for each VCSEL device at various substrate temperatures, demonstrating peak optical output power per device exceeding 50 mW.

[0041] Referring to FIG. 8, an optical microscope photograph of a portion of a 1200 dpi laser array 170 utilizing a common-anode multi-aperture pixel design is shown, according to an embodiment. The process direction 102 is indicated by a document icon 101. This design uses a common-anode architecture in which each address line 115 in the array contains multiple electrically connected apertures 175 to achieve a larger effective overall aperture size. The two-aperture "pixels" 175 in this embodiment can fit within a 1200 dpi pitch, yet each pixel (VCSEL 110) can emit more than 50 mW of optical power, as shown in the graph 180 provided in FIG. 9, which plots optical power versus current. The pixels can be arranged in four interdigitated columns addressed from the top and bottom sides.

[0042] The interdigitated pixel arrangement in Figures 1, 6, and 8 effectively creates a tighter linear pitch in the "cross-process" direction. In printing applications, an image can be formed row by row as the media traverses across the laser array in the "process direction," which is along the direction of the address lines. Each row of semiconductor lasers 110 can form a portion of the image. Because each row is spatially separated from the other rows, a time delay can be established between the formation of a portion of the image from one row and the formation of other portions from other rows. In Figure 8, for example, the pixel from the top row must be located adjacent to the pixel on the bottom row, followed by the pixel next to the top row and the pixel immediately above the bottom row. If these rows are labeled A, B, C, and D from top to bottom, and the media moves from bottom to top along the process direction, the laser in row A must fire after the laser in row D by a time delay equal to the distance between row A and row D divided by the speed of media movement. The image frames provided to columns A-D must be phase delayed in order for the images to be properly stitched together. The process direction print resolution can most conveniently be made the same as the cross-process direction print resolution when the separation between columns is a multiple of the cross-process pixel spacing.

[0043] Referring to FIG. 10A, an optical microscope photograph of a portion of a 1200 dpi laser array 190 utilizing a common-anode, three-aperture pixel design is shown, according to an embodiment. FIG. 10B shows a closer view of the three-aperture pixel of FIG. 10A, revealing six levels of stacking in the process direction, according to an embodiment. The process direction 102 in both figures is again indicated by the flow of document icons 101. This design employs a common-anode architecture, in which each address line 115 in the array encompasses three electrically connected apertures 195 to achieve a larger effective overall aperture size. A six-level stacking scheme in the process direction can be implemented to accommodate the emitters 110. The timing between activation of horizontally adjacent pixels can be implemented in the driving software. With appropriate timing that accounts for the relative motion of the imaged member and the laser, quasi-one-dimensional positioning of the laser can result in one-dimensional printed lines.

[0044] Mounting, cooling, driving, and imaging VCSEL array chips Due to the close spacing between lasers in such arrays, thermal crosstalk can be a problem, as the heat from each laser affects the performance of nearby lasers. Also, the aggregate power draw from many high-power lasers operating within a small area results in a high heat load density that must be dissipated. If not dissipated, the increased temperature will result in a reduction in optical output power and may damage the lasers.

[0045] These challenging thermal management issues can be addressed by developing a direct die-attach packaging approach, in which the laser array chip is die-attached directly onto a 3D mechanical block instead of a conventional planar submount. The mechanical block can incorporate embedded cooling fluid channels for flowing a cooling fluid, such as chilled water or ethylene glycol, which serves as the cathode electrical contact for the laser chip. The block can be thought of as a 3D submount with a built-in heat sink. The 3D submount also features integrated slots for the driver chip or electrical interposer, and mounting holes for the optics mount. Alternatively, the submount can include a heat pipe.

[0046] 11, a photograph 230 of the back view of a mechanical block is shown illustrating how cooling fluid conduits 233 / 235 may be attached to the mechanical block 220, according to an embodiment, and also illustrating how integral mounting holes may be formed in the mechanical block 220 for mounting optical elements. Cooling fluid channels 236 (dashed lines) may be embedded within the body of the mechanical block 220 and may be fabricated to direct coolant near the heat source for efficient heat removal. FIG. 11 also illustrates integral mounting holes 237 that may be provided for mounting optical elements used to image the laser beam.

[0047] Converging Optical System Because the optical output from a surface-emitting laser is divergent, focusing optics are typically required to structure the light beam and form an image. Several commercially available GRIN lens arrays, sold under the name SELFOC Lens Arrays (SLAs), can be constructed and used for this purpose. SLAs are well suited for this application because they allow the optical elements to be arranged in a linear configuration to image a set of laser elements, which are also arranged in a linear array, such as in the application presented herein. The "base cells" of the lens can be arranged in a linear array for this purpose.

[0048] SLA is a device that can be used to project a 1:1 image from a source onto a substrate. These devices are typically quasi-one-dimensional and are used in scanning applications such as photocopiers, scanners, printers, and fax machines. SLA is typically commercially available with two rows of gradient index optical elements coupled together in a predetermined format, and can be used in some printing applications, such as LED print bars. Each optical element collects light from a source and projects it onto the substrate. The images from all the optical elements are overlaid to form a projection of the source on the substrate. SLA is attractive because it can be made relatively large, making it usable for printing applications that typically require wide printing widths. Commercially available SLAs are approximately 12 inches wide. According to this embodiment, if a significantly wider printing width is required, several SLAs can be stitched together along the cross-process direction, or longer custom SLAs can be fabricated, or a complete VCSEL print bar can be staggered for use in a wide-width Dali printing process.

[0049] Referring to FIG. 12A, a diagram of two rows of SLA is shown. One problem with SLA is that incident light is either trapped by the optical elements 240 or absorbed by the binder 241 used to secure the optical elements 240. Ideally, the binder would be transparent to laser light, especially near-infrared light. Approximately 26% of the incident light can be absorbed by the binder 241. Therefore, the optical element fill factor is 2pi() / (4+2 *sqrt(5)) = 74%. Many imaging applications require very little power, so losing 26% of the light is not a problem. However, applications such as thermal processes (e.g., patterned sintering or evaporation) require high optical power. For applications requiring high power, this can create two problems: the SLA can get hot, requiring a system and optical design that can withstand the heat, and energy is wasted by the binder 241, thus requiring more power from the source element to achieve the desired thermal response. An overall light utilization of greater than 50% can be considered sufficient for many applications, including thermal processes.

[0050] Referring to FIG. 12B, a solution that can overcome the absorption problem with currently available SLA is to provide an SLA design in which the binder can be replaced with a transparent polymer 242. Using this type of binder can allow diffused light to pass through the SLA and be delivered to the substrate. The thermal process is often threshold-dependent. While the entire area can be heated, the desired effect is only seen when enough energy is present to initiate the thermal process. The diffused light can act as a preheat or postheat to provide a thermal offset to the imaged area. This can allow some percentage of the 26% lost light to be used in the thermal process and can help keep the SLA cool. Scattering elements 243 can also be incorporated into the binder to achieve light diffusion. Referring to FIG. 12C, a geometry is shown that can achieve more diffuse light compared to the geometry shown in FIG. 12B, which can provide more focused light.

[0051] Referring to FIG. 12D , a three-point perspective view 243 of an image-forming optical system including a four-row GRIN lens array that can be used with the VCSEL array described herein is shown, according to an embodiment. FIG. 12D illustrates an exemplary implementation utilizing a four-row GRIN lens array. Light paths 244 from each laser 110 can traverse several lens elements 245 and converge onto an image plane 247. FIG. 13 shows a graph 249 of calculated transmission efficiency versus beam divergence for various laser spatial mode profiles. Optical throughput can be limited by the imperfect fill factor of the GRIN lens array, as light that lands on the material in the gaps between the cylindrical optical elements is lost. Because divergent light not captured by the lens array is also lost, it is beneficial to use enough rows for the lens to ideally capture all of the light emanating from the VCSEL array.

[0052] More lens arrays can be constructed from a commercially available two-row SLA by removing the cladding from one side of the SLA, polishing away the cladding residue, and pressing two modified SLAs together. Referring to Figure 14A, a photograph 250 of a four-row SLA constructed from two modified two-row SLAs is shown, according to an embodiment. Referring to Figure 14B, an optical microscope photograph 255 of the combined two-row SLA 250 shown in Figure 14A is shown.

[0053] Alternative focusing optics In many cases, the desired printing width oversizes a traditional imaging system. Instead of using an SLA to focus the image 110 of the individual VCSEL lasers of the laser array 100 onto the blanket cylinder 266, it may be possible to use a different optical element, such as a traditional focusing lens 263. The combination of these types of lenses creates an inverted image of the target. Referring to FIG. 15A, a block diagram of a staggered imaging system 260 for focusing the output from the VCSEL laser array 100 is shown, according to an embodiment. As shown in FIG. 15A, it may be necessary to stagger the individual imaging systems 100 in a sawtooth pattern. Each row in the staggered system is activated with an appropriate timing delay 265 (e.g., t, t+Δt, t+Δt) so that the aggregate exposures made on the moving imaging member 266 are properly stitched to form the intended image.

[0054] Referring to FIG. 15B, an example of VCSEL scroll timing is shown using a two-aperture, four-column VCSEL laser array 170 (see FIG. 8 ), where a document 101 is processed at 1 m / s in the process direction 102 with 55 μm column spacing (center-to-center) between the VCSEL columns. As the document 101 is processed in the process direction 102, pixels in each column illuminate at different times according to the reference image to accommodate the distance between pixels based on their column assignment. Column 1 pixels are shown illuminating at a timing equal to 0.00 μs, while column 2 pixels are shown illuminating at 55.00 μs, column 3 at 110.00 μs, and column 4 at 165.00 μs. Therefore, accounting for the described delays can enable accurate image stitching during document processing.

[0055] Referring to Figure 16, a feathered imaging system 270 for focusing the output from the laser array 100 is shown, according to an embodiment. Focusing the output can be achieved by combining the beams using a beam combiner, such as polarizing optics 274 or a dichroic mirror, or both, to interleave the individual laser arrays 271 / 272 into an at least partially shared imaging path 275 onto the imaging member 266 (e.g., a drum), as shown in Figure 16. Combinations of polarizing and spectral beam combiners can be used to combine images, as well as cascades of beam combiners.

[0056] Referring to FIG. 17 , a block diagram of an interposer chip architecture 300 is shown that fans out tightly pitched contact pads 315 on a laser array 100 to wider pitched pads 325 on a PCB or driver chip, according to an embodiment. For high-resolution printing applications, such as 1200 dpi or higher, the required laser array pitch is very tight compared to the typical dimensions of pads and pad spacing on state-of-the-art PCBs. In some implementations, an interposer chip 300 can be used that fans out the electrical contacts 315 from the laser chip 100 to match a set of wider pitched contact pads on the PCB or driver chip. FIG. 17 shows an example embodiment in which an interposer is used to fan out contact pads 315 from 42 μm pitch to 100 μm pitch pads 325. This interposer design can be used on both sides of a laser chip to address an interdigitated array of lasers 100 on a pitch of 1200 dpi.

[0057] There are alternative interposer designs in which the contact pitch can be fanned in rather than fanned out. In such designs, the VCSEL array pads can be mapped to corresponding tighter pitch pads, for example, on the outputs of the driver chip (ASIC). The fan-in arrangement allows the driver chip to be smaller than the laser array chip, thus providing placement tolerance when aligning and tiling the driver chip to address the tiled laser array chips 100 as in FIG. 3.

[0058] Thinning of the substrate In certain applications, the ability to bond the laser array chip 210 directly onto a large, highly thermally conductive block 220 is essential to prevent thermal overload, as conventional 2D planar submounts add unacceptable thermal resistance between the laser chip 210 and the heat sink. In the presented cooling design, as described with respect to FIG. 11 , the highly concentrated heat generated within a small area of ​​the laser chip 210 can quickly enter the copper block 220 and spread over a large area of ​​the block 220, where it can be dissipated from the system via the coolant fluid flowing at high speed through the tubes 233 / 235.

[0059] Because semiconductor laser substrates typically have a high thermal resistance compared to metal blocks, the substrate can represent a significant bottleneck for heat flow from the heat generated by the laser. Thermal modeling indicates that, assuming a coolant flow rate of 4 liters per minute, thinning the substrate from a conventional 150 μm thick layer to 40 μm can reduce the temperature of the laser during operation by 12°C. This translates to an improvement in optical output power of approximately 10%. Using a thinner substrate, with a substrate thickness of 20 μm, can further reduce the laser temperature.

[0060] FIG. 18A shows a graph 340 of calculated temperature versus substrate thickness at various locations on the laser chip surface, according to an embodiment. The calculation assumes the laser array geometry shown in FIG. 1, the 3D submount design shown in FIG. 3, an ethylene glycol coolant temperature of −10° C., and a coolant flow rate of 4 L / min. FIG. 18B shows a diagram 345 of the temperature profile across the laser chip surface corresponding to the plot points shown in FIG. 18A. The device under test was an off-state device, but the temperature at that location was calculated when all lasers in the array were turned on at full power. This temperature is a measure of thermal crosstalk and the effect of neighboring lasers on the performance of the device under test.

[0061] Because a 20 μm thick layer is on the order of the thickness of a VCSEL epitaxial layer, the substrate thinning task is equivalent to removing the epi material from its native substrate and transferring it to a host metal substrate. Figures 19A-19E illustrate a process for accomplishing this task. The first step involves mounting a laser chip 355 containing a substrate 344, backside 356 facing up, onto a planar handle wafer 350, such as glass or silicon, using mounting wax 358, as shown in Figure 19A. Then, as shown in Figure 19B, the backside 356 is chemically mechanically polished, leaving only 20 μm of material. For GaAs substrates, the polishing step can be performed using sodium hypochlorite in conjunction with a rotating soft pad. Thickness control can be achieved using a mechanical stop designed to become part of the substrate holder. Alternatively, GaAs substrates can be selectively removed by using an etch-stop layer in the epilayer stack in combination with a chemical etchant that etches GaAs faster than the etch-stop layer. For example, a thin layer of AlGaAs can be used as an etch stop for NHOH / H2O2. Another example utilizes GaInP as an etch stop for HNO3 / H2O2. The handle wafer 350 can then be removed from the polishing jig and placed in a thin-film evaporator. In the evaporator, an n-type ohmic contact metal 357, such as AuGe, can be blanket deposited onto the polished backside 356 of the thinned substrate 344, as shown in FIG. 19C. The backside metal film can then be used as an electroplating seed for electroforming a layer of electroplated metal 359 to replace the removed substrate, as shown in FIG. 19D. The electroplated metal 359 can be, for example, a 50 μm thick layer of copper. The handle wafer 350 can then be removed by dissolving the mounting wax 358 in a solvent such as acetone, allowing the handle wafer 350 to be removed from the modified laser chip 355, as shown in FIG. 19E. This step can leave behind electroplated metal 359 that retains the transferred laser epi 333.The host substrate 356 and transferred laser array 333 can then be annealed to complete the n-side ohmic contact interface. The completed structure can then be die-attached to the mechanical block 220 as previously described.

[0062] VCSEL array printing application example While not intended to be a limitation on the applications of the embodiments disclosed herein, as previously mentioned, for example, the use of VCSEL arrays as individually addressable light sources in a Digital Architecture for Lithographic Ink (DALI) printing system, the DALI printing process has the advantage that the size, cost, and complexity of its most sophisticated component, the laser imager, is dramatically reduced.

[0063] 20 shows a schematic diagram of a prior art digital printing system 370 including an imaging member 266. The digital printing system 370 can be implemented as a system for variable lithography. The example imaging member 266 shown in FIG. 1 can be a drum, plate, or belt, or another now known or later developed configuration.

[0064] The imaging member 266 can be used to apply an ink image to the image receiving medium substrate 114 at the transfer nip 112. The transfer nip 112 can be formed by an impression roller 118, as part of an image transfer mechanism 160, that applies pressure toward the imaging member 266. The image receiving medium substrate 114 should not be considered limited to any particular composition, such as, for example, paper, plastic, or composite sheet film. The digital printing system 370 can be used to produce images on a wide variety of image receiving medium substrates.

[0065] The imaging member 266 can include a reimageable surface layer formed on a structural attachment layer, which can be, for example, a cylindrical core or one or more structural layers on a cylindrical core.

[0066] The digital printing system 370 can include a dampening system 122 with a series of rollers, which may be considered dampening rollers or dampening units, for uniformly wetting the reimageable surface of the imaging member 266 with dampening fluid. The purpose of the dampening system 122 is to deliver a layer of dampening fluid having a generally uniform and controlled thickness to the reimageable surface of the imaging member 266.

[0067] It is known that dampening fluids, such as fountain solution, may comprise primarily water, optionally with small amounts of isopropyl alcohol or ethanol added to reduce surface tension and lower the evaporation energy required to support subsequent laser patterning, as described in more detail below. Small amounts of certain surfactants may also be added to the dampening solution. Alternatively, other suitable dampening fluids may be used to improve the performance of ink-based digital lithography systems.

[0068] As the dampening fluid is dispensed onto the reimageable surface of the imaging member 266, the thickness of the dampening fluid can be measured using a sensor 125 that can provide feedback to control the dispensing of dampening fluid onto the reimageable surface of the imaging member 266 by the dampening water system 122.

[0069] After a precise and uniform amount of dampening fluid has been applied to the reimageable surface of the imaging member 266 by the dampening fluid system 122, the optical patterning subsystem 130 may be used to selectively form a latent image in the uniform dampening fluid layer, for example, by imagewise patterning the dampening fluid layer with laser energy. Typically, dampening fluid may not efficiently absorb optical energy (IR or visible). The optical patterning subsystem 130 may be implemented as or include a light source 131 (e.g., a vertical cavity surface emitting (VCSEL) array, a light emitting diode (LED) array, a laser light source emitting a pixelated light beam as a pixelated line laser beam, or a modulated laser line source).

[0070] The reimageable surface of the imaging member 266 ideally absorbs most of the laser energy (visible or invisible, such as IR) emitted from the optical patterning subsystem 130 proximate the surface to minimize energy wasted in heating the dampening fluid and to minimize lateral spread of heat to maintain high spatial resolution. Alternatively, a suitable radiation-sensitive component may be added to the dampening fluid to aid in the absorption of the incident radiant laser energy. While the optical patterning subsystem 130 is described above as being or including a light source, such as a laser emitter, it should be understood that a variety of different systems may be used to deliver the optical energy to pattern the dampening fluid.

[0071] Mechanisms that affect the patterning process performed by optical patterning subsystem 130 are known in the art. Briefly, the application of optical patterning energy from optical patterning subsystem 130 can result in the selective removal of portions of the dampening fluid layer.

[0072] After patterning the dampening fluid layer by the photo-patterning subsystem 130, the patterned layer on the reimageable surface of the imaging member 266 can be presented to the inker subsystem 145. The inker subsystem 145 can be used to apply a uniform layer of ink over the dampening fluid layer and the reimageable surface layer of the imaging member 266. The inker unit 145 can further include a heated ink bath, the temperature of which can be regulated by a temperature control module (not shown in FIG. 20). The inker subsystem 145 can use an anilox roller to meter offset lithographic ink onto one or more ink-forming rollers that can contact the reimageable surface layer of the imaging member 266. Separately, the inker subsystem 145 can include other conventional elements, such as a series of metering rollers, to provide a precise delivery rate of ink to the reimageable surface. The inker subsystem 145 can deposit ink into pockets representing the imaged portions of the reimageable surface, while the ink on the non-formatted portions of the dampening fluid does not adhere to those portions.

[0073] The cohesiveness and viscosity of the ink present in the reimageable layer of the imaging member 110 can be altered by several mechanisms. One such mechanism can involve, for example, the use of a rheology (complex viscoelastic coefficient) control subsystem 155. The rheology control system 155 can, for example, form a partially crosslinked core of ink on the reimageable surface to increase ink cohesion to the reimageable surface layer. Curing mechanisms can include optical or photocuring, thermal curing, drying, or various forms of chemical curing. Cooling can be used to alter rheology through several physical cooling mechanisms as well as by chemical cooling.

[0074] The ink can then be transferred from the reimageable surface of the imaging member 266 to the image receiving medium substrate 114 using the transfer subsystem 160. Transfer occurs when the substrate 114 passes through the nip 112 between the imaging member 266 and the impression roller 118 such that the ink in the voids of the reimageable surface of the imaging member 266 comes into physical contact with the substrate 114. If the ink's adhesion has been modified by the rheology control system 155, the modified adhesion of the ink causes the ink to adhere to the substrate 114 and separate from the reimageable surface of the imaging member 266. Careful control of the temperature and pressure conditions at the transfer nip 112 can enable ink transfer efficiencies of greater than 95% from the reimageable surface of the imaging member 266 to the substrate 114. While some dampening fluid may also wet the substrate 114, the amount of such dampening fluid is minimal and quickly evaporates or is absorbed by the substrate 114.

[0075] It should be appreciated that in certain offset lithography systems, an offset roller (not shown in FIG. 20 ) may first receive the ink image pattern and then transfer the ink image pattern to the substrate according to known indirect transfer methods. After the transfer of most of the ink to the substrate 114, residual ink and / or residual dampening fluid must be removed from the reimageable surface of the imaging member 266, preferably without scraping or abrading the surface. An air knife may be used to remove the residual dampening fluid. However, it is expected that some ink residue may remain. Removal of such remaining ink residue may be achieved through the use of some form of cleaning subsystem 172. The cleaning subsystem 172 may include at least a first cleaning member, such as a tacky or slightly tacky member, in physical contact with the reimageable surface of the imaging member 266, which removes residual ink and small amounts of remaining surfactant compound from the dampening fluid on the reimageable surface of the imaging member 266. The tacky or slightly tacky member can then be contacted with a smooth roller to which residual ink can be transferred from the tacky or slightly tacky member, after which the ink is stripped from the smooth roller by, for example, a doctor blade.

[0076] Other mechanisms can facilitate cleaning of the reimageable surface of the imaging member 266. However, regardless of the cleaning mechanism, cleaning residual ink and dampening fluid from the reimageable surface of the imaging member 266 can be essential to preventing so-called "ghosting." After cleaning, the reimageable surface of the imaging member 266 can again be presented to the dampening system 122, which can supply a fresh layer of dampening fluid to the reimageable surface of the imaging member 266, and the process can be repeated.

[0077] In the prior art digital printing system 370 shown in Figure 20, a blanket 113 (i.e., an "imaging cylindrical blanket" or "imaging blanket") is shown. An imaging member 266 in the form of a printing plate can surround the cylindrically shaped blanket 113. The blanket 113 with the imaging member 266 in the form of a printing plate shown in the example of Figure 20 can rotate in the direction indicated by the curved arrow 117.

[0078] The ink must be compatible with the materials it comes into contact with, including the imaging member 266, the dampening fluid applied by the dampening system 122, and other cured or uncured inks. The ink must also meet all functional subsystem requirements, including wetting and transfer properties. Imaged ink transfer is challenging because the ink must quickly and uniformly wet the blanket material (e.g., the imaging member 266) and transfer from the blanket 113 to the substrate (112, 114, and 118). Because the cleaning substation can only remove a small amount of residual ink, image layer transfer must be highly efficient—at least 90%. Any ink remaining on the blanket after cleaning will result in unacceptable ghost images in subsequent prints. Naturally, ink rheology plays a key role in the ink's transfer properties.

[0079] The DALI printing system involves the use of high-power lasers in the DALI printing process and their ability to modulate them pixel by pixel to generate latent dampening solution images that can be used to ink the printing blanket. DALI systems can enable the digital printing of high-viscosity inks at high resolution. Such a high-quality printing process can combine the inherent advantages of high-pigment loading, low-solvent content, and inexpensive inks with the ability to print with these inks in a digital, fully customizable manner for each pixel of each print.

[0080] In the DALI printing process, a continuous thin layer (e.g., tens of nanometers) of dampening fluid can be deposited on the surface of the printing blanket to repel the transfer of ink to the blanket 113 (especially the imaging member 266). A high-power laser can be used to heat surface areas of the light-absorbing blanket, thereby evaporating the dampening fluid in an imagewise pattern. However, the laser must heat the blanket sufficiently to provide the latent heat of evaporation as well as the sensible heat to raise the fluid to its evaporation temperature (e.g., about 175°C). The evaporated areas can then be inked, and the ink can be transferred to a receiver medium.

[0081] Although existing DALI printing systems can enable digital printing of high-viscosity inks at high resolution, current DALI printing processes can be relatively expensive due to the cost of high-power lasers and their modulation devices. Thus, solutions such as those described with respect to the embodiments described herein are needed to significantly reduce costs for DALI printing systems.

[0082] Design drawings of the completed VCSEL array-based imaging member 380 are depicted in the perspectives presented in FIGS. 21A and 21B . The macro interposer PCB 225 is shown mounted to the VCSEL cooling block 220. The VCSEL array 210 is shown mounted to the VCSEL cooling block 220, and the GRIN lens array 240 is shown aligned with and positioned on the opposite side of the VCSEL array 210. In addition to the described elements, FIGS. 21A / 21B also include a vapor extraction unit 388 mounted on a vapor extraction mount 387 and positioned proximate to the focal region (output) of the GRIN lens array 240. In some embodiments, the vapor extraction unit 388 can include a vacuum blade 389 or a physical blade, or both. The vapor extraction unit 388 can extract dampening fluid vapor generated by selective laser heating during the dampening fluid digitally structuring process. Figure 21B shows the general location of wire bonds 382 and VCSEL interposers 381 / 384, as well as collection plane 360, which may be adjusted to typically be located on blanket cylinder 375. Figure 21A shows where vapor extraction adjustment 383 may occur. Additionally, as shown in Figure 11, cooling fluid conduits 233 may be attached to the VCSEL cooling block 220, which may provide coolant to the block.

[0083] Referring to FIG. 22, a block diagram 400 of an electronics module operating as part of a printing system is shown, according to an embodiment. The electronics module as shown can provide the system functionality of the application-specific integrated circuit (ASIC) driver chip 135 described with respect to FIG. 3 and in the subsequent discussion. In cooperation, the electronics modules as shown can enable a system for controlling and driving independently addressable semiconductor lasers. A computer 405 can be provided to convert an image into raw data and provide it to a control interface 410. The control interface 410 can then transmit the raw data and timing to driver electronics 415. The current driver 415 can convert the raw data and timing information provided by the control interface 410 into a regulated current signal. A VCSEL array 420 can then convert the current signal into light used to illuminate the imaging member 266 (see FIG. 15A).

[0084] Referring to FIGS. 23A-23B, a block diagram 450 is shown, which is just one example of functional states that may be implemented in the control interface circuit. The control interface circuit can take a stream of image data for each column of the VCSEL device from a computer and convert them into timing signals and appropriately timed data for the current driver circuits to power the VCSEL devices to generate the desired print output. The interface circuit requires the stream of image data as well as system information, including, but not limited to, print media speed, print media acceleration, deceleration, and device-to-device variations in VCSEL power. In the idle state 460, the control interface typically waits for image data from the computer. In the print setup state 470, the control interface circuit receives and buffers pre-formatted image data streams from the computer for each VCSEL column in preparation for generating the desired print output. In the line printing states 451-454, the data for each column of the four-column VCSEL array responds to the sub-frame delay 458 data to appropriately stitch and generate a timed image on the drum. Each line print can process data and timing information using the Display Line, Send Next Line, and Memory Access modules based on image processing data received from the modules in Print Setup 470. After processing the document, the system can return 459 to the idle state 460 to await additional / new processing requirements.

[0085] Referring to FIG. 24 , a block diagram 500 is shown illustrating possible functionality in the major modules of a printing system incorporating the use of a VCSEL array, according to an embodiment. As shown in block 503, an image can be converted into four data streams (e.g., A, B, C, and D). Simultaneously, timing information can be converted into clock pulse values ​​and sent to FPGA memory, where a current set point can be set, as described in block 505. Image data can be stored in FPGA memory using DMA functions, as shown in block 510, while timing information can be retrieved from FPGA memory and stored in FPGA registers, as shown in block 513. The current set point information can then be stored in dot correction registers in the printing module in preparation for further document processing / rendering using the VCSEL, as shown in block 515.

[0086] Referring to FIG. 25 , another block diagram 550 is shown illustrating possible functions of an electronic module of a printing system incorporating the use of a VCSEL array, according to an embodiment. As noted in block 555, print start and stop operations can be initiated by a computer after the steps described herein with respect to FIG. 24 . As noted in block 560, image data can be retrieved from FPGA memory for each line to be printed, formatted, and shifted from the FPGA to the module. Simultaneously, as noted in block 563, a control (CNTRL) signal can be raised and lowered for each group (ABCD) based on timing values ​​stored in a register. Then, as noted in block 565, a current output can be activated according to the value of the grayscale register at the start of each line print cycle. Furthermore, the next line data can be shifted into the grayscale register while the current is being output.

[0087] In summary, structures and methods for realizing tightly pitched, independently addressable, high-power surface-emitting laser arrays are disclosed herein, along with associated components and methods for enabling the use of such laser arrays in printing applications.

[0088] It will be understood that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. It will also be understood that various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements may be subsequently made by those skilled in the art and are intended to be encompassed by the following claims.

Claims

1. 1. A laser imager for a printing system, comprising: more than 100 independently addressable lasers arranged in a linear array on a common substrate chip, the independently addressable lasers being vertical cavity surface emitting lasers (VCSELs) comprising oval apertures and two or more apertures per control channel; a dedicated control channel associated with the address trace lines for facilitating communication from driver electronics with each of said independently addressable lasers; an optical element configured to capture and focus light from the independently addressable lasers, the optical element also being arranged in a linear lens array and operating in conjunction with the independently addressable lasers to provide a power of 20 W / mm 2 and an optical element for imaging the independently addressable laser onto the imaging member with a light intensity greater than .

2. 10. The laser imager of claim 1, wherein the independently addressable lasers share a cathode through a substrate of the common substrate chip.

3. The laser imager of claim 1 , wherein the optical element is embodied in a GRIN lens array.

4. 10. The laser imager of claim 1, wherein the common substrate chip is coupled to a mechanical block containing at least one cooling fluid channel therein and configured to control the temperature of the independently addressable lasers during their operation.

5. 10. The laser imager of claim 1, further comprising a drive electronics chip that provides power to the independently addressable lasers from the driver electronics via a respective dedicated control channel associated with the address trace line for each of the independently addressable lasers.

6. 6. The laser imager of claim 5, further comprising two or more common substrate chips tiled side-by-side and stitched together to provide an imager that is at least 11 inches wide.

7. 7. The laser imager of claim 6, further comprising the two or more common substrate chips tiled in a staggered arrangement and stitched together.

8. 7. The laser imager of claim 6, wherein the linear density of the independently addressable lasers is greater than 10 laser pixels per millimeter.

9. 10. The laser imager of claim 1 further comprising a facility for extracting dampening fluid.

10. 10. The laser imager of claim 1, wherein the independently addressable lasers emit light in the wavelength range of 550 nm to 1000 nm.

11. 10. The laser imager of claim 1, wherein said optical element creates a non-inverted image of said independently addressable lasers in said laser array.

12. 10. The laser imager of claim 1, wherein each address trace line associated with each control channel for each of the plurality of independently addressable lasers further includes two or more apertures operable in concert to achieve a larger effective aperture size.

13. A laser imager as described in claim 12, wherein the two or more apertures that can operate together to achieve the larger effective aperture size are two-aperture pixels.

14. 1. A laser imager for a printing system, comprising: more than 100 independently addressable lasers arranged in a linear array on a common substrate chip, the independently addressable lasers being vertical cavity surface emitting lasers comprising oval apertures and two or more apertures per control channel; driver electronics embodied in an application specific integrated circuit (ASIC); a dedicated control channel associated with an address trace line for facilitating communication from said driver electronics with each of said independently addressable lasers; Optical elements arranged in a linear lens array and configured to capture and focus light, with a power of 20 W / mm 2 and an optical element for imaging the independently addressable laser onto the imaging member at a greater light intensity.

15. 15. The laser imager of claim 14, wherein the independently addressable lasers are tiled next to each other on the common substrate to provide stitched imaging on the imaging member at least 11 inches wide at at least 300 dots per inch.

16. 16. The laser imager of claim 15, wherein the common substrate chip is coupled to a mechanical block containing at least one cooling fluid channel therein and configured to control the temperature of the independently addressable lasers during their operation.

17. 1. A laser system comprising over 100 independently addressable lasers tiled in a linear laser array on a common substrate chip, dedicated control channels associated with address trace lines for facilitating communication from driver electronics with each of said independently addressable lasers, and optical elements configured to capture and focus light from said independently addressable lasers, wherein said independently addressable lasers are vertical cavity surface emitting lasers comprising an oval aperture and two or more apertures per control channel, said optical elements being arranged in a linear lens array and operating in conjunction with said independently addressable lasers to provide a laser output of 20 W / mm 2 creating an image from said independently addressable laser on an imaging member at a greater light intensity; and depositing dampening fluid provided from a vapor phase module onto a surface of the imaging member; digitally patterning the dampening fluid in an image based on current provided by the driver electronics using laser light emitted from the linear laser array, wherein the imaging member becomes heated by the light and the dampening fluid selectively evaporates from hotter portions of the imaging member and remains in cooler portions of the imaging member as a negative image of the image on the imaging member based on the digital pattern laser emitted from the light of the linear array through the optical element; extracting vapors of the dampening solution via a vacuum source to prevent recondensation of the dampening solution on the imaging member; transferring high viscosity ink from an inking source to the imaging member, the high viscosity ink forming and being removed on the imaging member, leaving a dampening solution on the imaging member; transferring said high viscosity ink from said imaging member to a substrate, leaving a 1:1 copy of said image on said substrate.

18. The method described in claim 17, wherein two or more common substrate chips carrying surface-emitting lasers among the independently addressable lasers are tiled adjacent to each other to provide an imager at least 11 inches wide.

Images